1. Field of the Invention
The present invention relates to a thin-film magnetic head having a coil layer provided between core layers. In particular, the present invention relates to a thin-film magnetic head suitable for narrower track widths and to a method for making the thin-film magnetic head in which the front end of the upper core layer can be precisely formed so as to have a track width Tw.
2. Description of the Related Art
FIG. 24 is a longitudinal cross-sectional view showing a structure of a conventional thin-film magnetic head. This thin-film magnetic head is an inductive write head and is mounted at the trailing end of a slider of a floating magnetic head which opposes recording media such as hard disks.
The thin-film magnetic head has a lower core layer 1 composed of a magnetic material such as a NiFe alloy. A gap layer 3 composed of a nonmagnetic material, such as alumina (Al2O3) or SiO2, is formed on the lower core layer 1. Furthermore, an insulating layer 7 composed of an organic material such as a resist material is formed on the gap layer 3.
A spiral coil layer 4 composed of a conductive material having low electrical resistance such as copper is formed on the insulating layer 7. The coil layer 4 is provided so as to surround a base end 6b of an upper core layer 6, although only part of the coil layer 4 is depicted in FIG. 24. The coil layer 4 is covered with a coil-insulating layer 5 composed of an organic material or the like. The upper core layer 6 is formed on the coil-insulating layer 5 by plating a magnetic material such as Permalloy. A front end 6a of the upper core layer 6 is jointed to the lower core layer 1 with the gap layer 3 provided therebetween at a face opposing a recording medium to define a magnetic gap having a gap length Gl. The base end 6b of the upper core layer 6 is magnetically coupled with the lower core layer 1 via a hole formed in the gap layer 3.
The width of the front end 6a of the upper core layer 6 in the track width direction (X direction in the drawing) defines a track width Tw. Trends toward recent high-density recording require the formation of a smaller track width Tw.
In the inductive write head, a recording current applied to the coil layer 4 induces a recording magnetic field to the lower core layer 1 and the upper core layer 6. A leakage magnetic field from the magnetic gap portion between the lower core layer 1 and the front end 6a of the upper core layer 6 is recorded on a recording medium such as a hard disk as a magnetic signal.
The upper core layer 6 of the thin-film magnetic head is formed by a frame plating process. FIG. 25 shows a step for forming the upper core layer 6. The gap layer 3 is formed on the lower core layer 1, and the insulating layer 7 is formed on the gap layer 3 with a predetermined gap depth T1 in the height direction (Y direction in the drawing) from the face opposing a recording medium. Next, the coil layer 4 is formed on the insulating layer 7. After the coil layer 4 is covered by the coil-insulating layer 5, a plating underlayer 9 composed of a magnetic material such as a NiFe alloy is formed over the exposed front portion of the gap layer 3 and the coil-insulating layer 5.
A resist layer 8 is formed on the plating underlayer 9 and is exposed and developed to form a pattern of the upper core layer 6 on the resist layer 8. A magnetic layer is formed by plating on the exposed plating underlayer 9 and the remaining resist layer 8 is removed. The upper core layer 6 shown in FIG. 24 is thereby completed.
In the above conventional thin-film magnetic head, the formation of the upper core layer 6 has the following problems.
As shown in FIG. 25, a protrusion having a height H3 from the surface of the gap layer 3 is formed by depositing the insulating layer 7, the coil layer 4, and the coil-insulating layer 5 on the lower core layer 1. When the resist layer 8 is coated on the plating underlayer 9, the thickness H1 of the resist layer 8 is significantly large on the front portion of the lower core layer 1. Moreover, the thickness of the resist layer 8 is not uniform.
Thus, focusing in the exposure and develop step of the resist layer 8 is difficult, and thus, a precise pattern of the upper core layer 6 cannot be formed in the resist layer 8. Accordingly, the uneven thickness causes a decrease in precision of the patterning.
The front end 6a of the upper core layer 6 is defined by the track width Tw as described above. To satisfy future trends towards high-density recording, the track width Tw must be smaller. Since the thickness H1 of the resist layer 8 is significantly large at a portion to form the front end 6a of the upper core layer 6, a large focal depth is required in the exposure and develop step to form a pattern in the resist layer 8 having the thickness H1. Such a large focal depth requires light having a shorter wavelength in the exposure and develop step. The light having the shorter wavelength causes a decrease in resolution and the width of the front end 6a of the resulting upper core layer 6 is inevitably larger than the track width Tw.
Since the thickness of the resist layer 8 is not uniform due to the protrusion formed by the coil-insulating layer 5, the insulating layer 7, and the coil layer 4 on the lower core layer 1, irregular reflection readily occurs in the exposure and develop step. Thus, the pattern formed in the resist layer 8 is distorted. As a result, the front end 6a of the upper core layer 6 cannot have the track width Tw.
It is an object of the present invention to provide a thin-film magnetic head which has a front end, defined by the track width Tw, of an upper core layer and can be used for narrower tracks.
It is another object of the present invention to provide a method for making the same.
An aspect of the present invention relates to a thin-film magnetic head comprising a lower core layer; a lower magnetic pole layer formed independently of or integrally with the lower core layer; a nonmagnetic gap layer extending from a face opposing a recording medium on the lower magnetic pole layer; an upper core layer in contact with the upper face of the gap layer; and a coil layer lying behind the lower magnetic pole layer in the height direction, the coil layer being covered with a coil-insulating layer and inducing a recording magnetic field in the lower core layer and the upper core layer; wherein the upper core layer in contact with the gap layer has a track width Tw at an exposed face opposing a recording medium, and the upper core layer extends on the coil-insulating layer.
This configuration reduces the protrusion of the surface for forming the upper core layer compared to conventional configurations, and precisely forms the front end with the track width Tw of the upper core layer within a predetermined range. Since the lower magnetic pole layer is formed on the lower core layer, the coil layer is formed on the lower core layer which is indented from the surface of the lower magnetic pole layer. The upper core layer is formed over the lower magnetic pole layer and the coil-insulating layer covering the coil layer. Thus, the protrusion of the coil-insulating layer is determined based on the surface of the gap layer formed on the lower magnetic pole layer.
In contrast, a lower magnetic pole layer is not formed on a lower core layer in conventional configurations. Thus, the protrusion of the coil-insulating layer is determined based on the gap layer formed on the lower core layer.
Accordingly, the protrusion of the coil-insulating layer in the present invention can be reduced by a the thickness of the lower magnetic pole layer formed at least on the lower core layer. As a result, the thickness of a resist layer used in the formation of the upper core layer can be reduced in the vicinity of the front end having a track width Tw. Moreover, the resist layer can be more uniformly formed over the entire region compared to the conventional configurations, improving resolution and reducing irregular reflection. The front end of the upper core layer is thereby formed precisely within a predetermined track width Tw.
Preferably, the gap layer has the track width Tw, and the lower magnetic pole layer has the track width Tw at a position in contact with the gap layer. In a preferred embodiment of this configuration, the lower magnetic pole layer is formed independently of the lower core layer and has a base portion and a protruding portion extending toward the upper core layer, the width of the protruding portion is smaller than that of the base portion, and the upper face of the protruding portion is in contact with the gap layer. Preferably, the lower magnetic pole layer has sloping faces extending from the bottom corners of the protruding portion toward directions departing from the upper core layer at both sides in the track width direction. In addition, the lower core layer may have sloping upper faces continuing from the sloping faces of the lower magnetic pole layer.
Alternatively, the lower magnetic pole layer may be formed independently of the lower core layer and may be rectangular or trapezoidal in which the width of the bottom in contact with the lower core layer is larger than the width at the top in contact with the gap layer, and the lower core layer may have a protruding portion having sloping upper faces continuing from the sloping faces of the lower magnetic pole layer. Preferably, the upper face of the lower core layer has sloping faces extending from the bottom corners of the protruding portion so as to depart from the upper core layer in the track width direction.
Alternatively, the lower magnetic pole layer may be integrally formed with the lower core layer and protrudes from the lower core layer. In such a case, preferably, the lower core layer has sloping upper faces extending from the bottom corners of the protruding lower magnetic pole layer toward directions departing from the upper core layer at both sides in the track width direction.
The protruding portion and the sloping faces of the lower magnetic pole layer and the protruding portion and the sloping faces of the lower core layer can adequately reduce write fringing.
In the present invention, the lower magnetic pole layer may be formed integrally with the lower core layer.
The gap layer may extend over the lower magnetic pole layer and the lower core layer behind the lower magnetic pole layer in the height direction.
The gap layer formed on the lower core layer may function as an insulating layer between the coil layer and the lower core layer.
Preferably, the thin-film magnetic of the present invention further comprises a gap-depth-defining insulating layer provided on the lower magnetic pole layer and extending from a position which is distant from a face opposing a recording medium by a predetermined distance in the height direction.
Alternatively, the thin-film magnetic head of the present invention further comprises a gap-depth-defining insulating layer extending from a position distant from a face opposing a recording medium by a predetermined distance in the height direction, wherein the gap-defining insulating layer and an insulating layer lying between the coil layer and the lower core layer are integrally formed.
Preferably, the gap-distance-defining insulating layer comprises an organic insulating material.
Preferably, the coil-insulating layer comprises an organic insulating material.
A second aspect of the present invention relates to a method for making a thin-film magnetic head comprising the steps of:
(a) forming a lower magnetic pole layer on a lower core layer from a face opposing a recording medium to a position distant from the face opposing the recording medium by a predetermined length in the height direction;
(b) forming a nonmagnetic gap layer over the lower magnetic pole layer and the lower core layer behind the lower magnetic pole layer in the height direction;
(c) forming a coil layer on the gap layer directly or separated by an insulating layer provided therebetween;
(d) covering the coil layer by a coil-insulating layer; and
(e) forming an upper core layer over the coil-insulating layer and the lower magnetic pole layer so that the width of the upper core layer is equal to a track width at an exposed face opposing a recording medium.
In the above method, the lower magnetic pole layer is formed on the lower core layer. The lower magnetic pole layer can be formed directly on the lower core layer by plating without providing a plating underlayer. The formation of the coil etc is the same as that in conventional processes.
In the above method, the lower magnetic pole layer is formed on the lower core layer and the coil layer and the coil-insulating layer are formed on the lower core layer which is indented from the surface of the lower magnetic pole layer. Thus, the protrusion of the coil-insulating layer from the surface of the lower magnetic pole layer can be reduced.
The upper core layer is generally formed by a frame plating process. In the above method, a resist layer is formed on a surface for forming the upper core layer, that is, over the lower magnetic pole layer and the coil-insulating layer.
Since the protrusion of the coil-insulating layer from the surface of the lower magnetic pole layer can be suppressed compared to the conventional configurations, the thickness of the resist layer can be reduced on the lower magnetic pole layer and is uniform in the entire region. Thus, resolution in the exposure step is improved and irregular reflection is reduced. As a result, the front end of the upper core layer having the track width Tw can be precisely formed on the lower magnetic pole layer.
A third aspect of the present invention relates to a method for making a thin-film magnetic head comprising the steps of:
(f) forming planarization layers composed of an insulating material extending from a face opposing a recording medium along the height direction on two sides in the track width direction of a lower core layer;
(g) milling the surface of the lower core layer and the surfaces of the planarization layers along the height direction from a position distant from the face opposing a recording medium so that the height of these surfaces is less than the height of surfaces of other regions, in order to form a coil-forming area and to define a lower magnetic pole layer integrally protruding from the lower core layer at the face opposing a recording medium;
(h) forming a nonmagnetic gap layer over the lower magnetic pole layer and the coil-forming area;
(i) forming a coil layer on the gap layer in the coil-forming region, directly or with another insulating layer provided therebetween; and
(j) covering the coil layer by a coil-insulating layer;
(k) forming an upper core layer over the lower magnetic pole layer and the coil-insulating layer,
wherein the width of the upper core layer exposed at the face opposing a recording medium is a track width Tw.
In this method, a thick lower core layer is previously formed, and is etched away in an area for forming the coil layer. Thus, the lower core layer has a protruding portion at the face opposing a recording medium. This protruding portion corresponds to the lower magnetic pole layer. That is, in this method, the lower magnetic pole layer is integrally formed with the lower core layer.
This method is preferable to the above-mentioned method for forming the lower magnetic pole layer on the lower core layer, since the front end of the upper core layer can be more precisely formed within the track width Tw.
Since in this method, the planarization layers (for example, Al2O3 layers) are provided on both sides of the lower magnetic pole layer in the track width direction and the height of the planarization layers is the same as the surface of the lower magnetic pole layer. Thus, the resist layer having a thinner and more uniform thickness can be formed on the flat surface. As a result, the front end of the upper core layer can be formed more precisely within the track width Tw.
In the second aspect, the method comprises, instead of the steps (g), (h), and (i), the following steps:
(l) forming a nonmagnetic gap layer on the lower core layer and the porous layer;
(m) milling the gap layer, the lower core layer, and the planarization layers along the height direction from a position which is distant from the face opposing a recording medium so that the height of these surfaces is less than the height of surfaces of other regions, in order to form a coil-forming area and to define a lower magnetic pole layer which is integrated with and protrudes from the lower core layer and is provided with the gap layer thereon at the face opposing a recording medium;
(n) forming an insulating layer on the lower core layer and the planarization layers in the coil-forming region; and
(o) forming a coil layer on the insulating layer.
In these steps, the gap layer is formed over the lower core layer and the planarization layers, and then the lower core layer and the planarization layers are polished to form an area for forming the coil layer. Thus, the gap layer still remains on the lower magnetic pole layer after the polishing steps.
When the gap layer is formed on the lower core layer, the gap layer may be used as in insulating layer between the coil layer and the lower core layer, and the coil layer may be directly formed by patterning on the gap layer. In the above method, however, the gap layer on the lower core layer is removed for forming the coil layer. Thus, the insulating layer is formed on the lower core layer and then the coil layer is formed on the insulating layer.
Preferably, the method further comprises the following step, lying between the step (n) and the step (o), of:
(p) forming a gap-defining insulating layer at a portion distant from the face opposing a recording medium in the height direction at least on the lower magnetic pole layer.
Preferably, the method according to the second or third aspect further comprises the steps, subsequent to the step (e) or (k), of:
(q) removing the gap layer extending from the upper core layer having the track width Tw toward both sides in the track width direction;
(r) milling the upper face of the lower magnetic pole layer at both sides of the track width Tw so that the lower magnetic pole layer has a protruding portion having a width which is equal to the track width Tw at the junction with the gap layer; and
(s) forming sloping faces extending from both bottom corners of the protruding portion toward directions departing from the upper core layer along the track width direction on the lower magnetic pole layer.
Alternatively, in the step (s), both upper faces of the lower core layer and both upper faces, which are thereby exposed, of the upper core layer may be milled to form sloping faces of the lower core layer continuing from the sloping faces of the lower magnetic pole layer.
The method may further comprises the following steps, instead of the steps (r) and (s), of:
(t) milling both sides of the track width Tw of the lower magnetic pole layer in the track width direction so that the lower magnetic pole layer has a rectangular shape in which the width at the junction with the gap layer is equal to the track width Tw or a trapezoidal shape in which the width at the junction with the gap layer is larger than the width at the junction with the lower core layer; and
(u) forming sloping faces on the lower core layer, the sloping faces extending from both bottom corners of the lower magnetic pole layer toward directions departing from the upper core layer along the track width direction.
As described above, the protruding portion and the sloping faces of the lower magnetic pole layer and the protruding portion and the sloping faces of the lower core layer can adequately reduce write fringing of the thin-film magnetic head.